How to read two arguments in text file?

Question

I'm starting to program in python. I have a question about reading two files inside a text file my code.

arq = open("output.txt", "w")
count = 0
file_path = "/homescript/ASN.txt"
with open(file_path) as file:
    for line in file:
        line = line.rstrip()
        if 'AS' in line:
            count = count + 1
            print("set policy", line,"then accept",line, file=arq)
print ("\n Display return",count,"lines")

my text file contains:

AS0000
192.168.0.1/24
192.168.1.0/24

I need print ip address after "then accept"

Answer 1

You need to use the .readlines method to get the lines in the file, not just try to iterate from the entire file object. If you want a raw dump, use file.read() .

arq = open("output.txt", "w")
count = 0
file_path = "/homescript/ASN.txt"
with open(file_path) as file:
    for line in file.readlines():
        line = line.rstrip()
        if 'AS' in line:
            count = count + 1
            print("set policy", line, "then accept",line, file=arq)
print ("\n Display return", count, "lines")
arq.close()

Also don't forget to .close() the file.

Answer 2

arq = open("output.txt", "w")
count = 0
file = open("/homescript/ASN.txt", "r")
t = []
for line in file.readlines():
    line = line.strip()
    t.append(line)
for i in range(len(t)):
if 'AS' in t[i]:
    count = count + 1
    print("set policy", t[i], "then accept", t[i+1])
    print("set policy", t[i], "then accept", t[i+2])
print("\n Display return", count, "lines")

Answer 3

An easy way

count = 0
file_path = "/homescript/ASN.txt"

with open(file_path) as file, open("output.txt", "w") as arq:  # you can open several files at once
    lines = file.readlines()  # read all lines into a list
    for i in range(len(lines)):
        line = lines[i].rstrip() # extract i-th line
        if 'AS' in line:
            count += 1
            ip = lines[i + 1].rstrip()  # ip is in the following line
            print("set policy", line, "then accept", ip, file=arq)
            
print ("\n Display return", count, "lines")

As you can see, the code above reads the whole file and iterates over a list. If a line contains 'AS', the next line is extracted as the IP address. This is not the most pythonic solution, but for you, as a beginner, should be good enough.

---

A more pythonic one

With the pairwise from python 3 docs you can do it even more easily:

from itertools import tee

def pairwise(iterable):
    "s -> (s0,s1), (s1,s2), (s2, s3), ..."
    a, b = tee(iterable)
    next(b, None)
    return zip(a, b)

count = 0
file_path = "/homescript/ASN.txt"

with open(file_path) as file, open("output.txt", "w") as arq:
    for line, next_line in pairwise(file):
        if 'AS' in line:
            count += 1
            ip = next_line.rstrip()
            print("set policy", line, "then accept", ip, file=arq)      
            
print ("\n Display return", count, "lines")